Grass surfaces can be used for recreational purposes such as sports. Repeated use of grass surfaces can cause wear and damage to the surface, and so a turf manager charged with maintaining a grass surface must minimise the wear and damage as much as possible.
Different treatments are used to maintain grass surfaces; mowing is used to control the length of the grass, spiking is used for shallow aeration of the soil beneath the grass, scarification is used to remove thatch from the grass surface. and brushes are used to remove extraneous matter such as leaves from the surface of the grass.
All of the above types of grass treatment can be performed using grass treatment devices that have a rotating action moving over the grass surface. Typically, such grass treatment devices are mounted on a grass treatment machine such as a “triple mower”. A triple mower comprises three different grass treatment units. Referring to FIG. 1 herein, there is illustrated schematically a plan view of the layout of the grass treatment units of a prior art triple mower.
The triple mower comprises a first and second grass treatment unit 101, 102 disposed adjacent to each other and towards the front of the triple mower in the direction 103 of movement. A third grass treatment unit 104 is disposed behind the pair of grass treatment units 101, 102. There is a gap 105 between the first grass treatment unit 101 and the second grass treatment unit 102. As the triple mower moves, the third grass treatment unit 104 treats the grass that was previously in the gap 105 between the first grass treatment unit 101 and the second grass treatment unit 102.
Each grass treatment unit 101, 102, 104 has a corresponding hydraulic motor 106, 107, 108 that drives a grass treating device mounted on the grass treatment unit 101, 102, 104. Each grass treatment unit also comprises a first roller 109 and a second roller 110 (illustrated on the first grass treatment unit 101 but also on the second 102 and third grass treatment unit 104).
Due to the large number of different types of grass treatments that are required, it is expensive for a turf manager to purchase and store different grass treatment units for different operations such as mowing, scarification, spiking, brushing and so on. To ameliorate this problem, it is known to use a cassette system for grass treatment units. Using the cassette system, a turf manager has a set of grass treatment cassettes. Each cassette of the set of grass treatment cassettes is releasably mountable on the grass treatment unit, and each cassette of the set of cassettes comprises a different type of grass treatment device. For example, a set of grass treatment cassettes may comprise a mowing device, a scarification device, a power brush, and a spiker. When a turf manager wishes to perform a mowing operation a mowing cassette 111, 112, 113 is mounted onto each grass treatment unit on the triple mower. If the turf manager then wishes to perform a spiking operation, each mowing cassette is removed from each grass treatment unit and replaced with a spiking cassette 114, 115, 116.
Each motor 106, 107, 108 is connected to a drive shaft 114, 115. 116 that rotates the grass treatment device of the corresponding cassette 111, 112, 113.
By using the cassette system, the costs and storage space required for maintaining the required grass treatment tools is significantly reduced. Furthermore the operation of replacing one grass treatment device with another is much simplified as a cassette is replaced in a housing of the grass treatment unit rather than replacing the entire grass treatment unit. This allows the grass treatment unit to remain fixed to the grass treatment machine whilst the cassette is replaced for a different cassette that performs a different grass treatment function.
For surfaces such as golf greens, the “speed” of the green must be controlled. This can be done by careful mowing to obtain a required grass length. However, where a fast green is required the length of the grass must be short. If grass length is very short then it can easily become distressed or diseased, thereby damaging the properties of the green. It has been found that vibration rolling can be used to increase the speed of a green whilst maintaining a longer grass length, as it flattens minor imperfections in the grass surface.
A vibration roller comprises a roller that has a vibrating mechanism associated with it. The vibrating mechanism typically consists of a rotating shaft that has an off-centre weight. It is known from U.S. Pat. No. 5,261,213 to replace an entire grass treatment unit comprising a mower of a triple mower with a vibrating drum. However, the vibrating drum operates at a speed of around 5,000 rpm whereas a mower operates at a speed of around 2,500 rpm. Gearing in the housing of the grass treatment unit is therefore required to alter the speed of revolution. The vibrating drum is in direct contact with the ground and damping is required to isolate the vibrations of the vibrating drum from the housing of the grass treatment unit. A problem associated with this system is that it is expensive and bulky to store, as a set of entire grass treatment units dedicated solely to vibration rolling must be purchased and stored in addition to separate grass treatment units for other types of grass treatment operation.
A vibration roller cannot be incorporated into known cassette mechanisms as the vibrations would propagate throughout the triple mower causing damage to each grass treatment unit and to the drive motors 106, 107, 108. Furthermore the drive motors typically operate at a speed of 2,500 rpm and this speed is insufficient to give effective vibration rolling.